Beer-Lambert Law & Absorbance Calculator

Calculate absorbance, concentration, path length, or molar absorptivity.

Enter known values and select which parameter to calculate using the Beer-Lambert Law.

Examples

See how to use the Beer-Lambert Law for different scenarios.

Calculate Concentration from Absorbance

Beer-Lambert Law

Given A = 0.85, ε = 15000 L·mol⁻¹·cm⁻¹, l = 1 cm, find c.

Absorbance (A): 0.85

Concentration (c): mol/L

Path Length (l): 1 cm

Molar Absorptivity (ε): 15000 L·mol⁻¹·cm⁻¹

Parameter to Calculate: Concentration (c)

Calculate Absorbance

Beer-Lambert Law

Given c = 0.002 mol/L, ε = 15000 L·mol⁻¹·cm⁻¹, l = 1 cm, find A.

Absorbance (A):

Concentration (c): 0.002 mol/L

Path Length (l): 1 cm

Molar Absorptivity (ε): 15000 L·mol⁻¹·cm⁻¹

Parameter to Calculate: Absorbance (A)

Calculate Path Length

Beer-Lambert Law

Given A = 0.6, ε = 12000 L·mol⁻¹·cm⁻¹, c = 0.0005 mol/L, find l.

Absorbance (A): 0.6

Concentration (c): 0.0005 mol/L

Path Length (l): cm

Molar Absorptivity (ε): 12000 L·mol⁻¹·cm⁻¹

Parameter to Calculate: Path Length (l)

Calculate Molar Absorptivity

Beer-Lambert Law

Given A = 1.2, c = 0.001 mol/L, l = 1 cm, find ε.

Absorbance (A): 1.2

Concentration (c): 0.001 mol/L

Path Length (l): 1 cm

Molar Absorptivity (ε): L·mol⁻¹·cm⁻¹

Parameter to Calculate: Molar Absorptivity (ε)

Other Titles
Understanding Beer-Lambert Law & Absorbance: A Comprehensive Guide
Master the science of spectrophotometry and solution analysis.

What is the Beer-Lambert Law?

  • Definition and Formula
  • Physical Meaning
  • Importance in Chemistry
The Beer-Lambert Law relates the absorbance of light to the properties of the material through which the light is traveling. It is fundamental in spectrophotometry and analytical chemistry.
Beer-Lambert Law Formula
A = ε · c · l, where A is absorbance, ε is molar absorptivity, c is concentration, and l is path length.

Real-World Examples

  • A solution with higher concentration absorbs more light.
  • Longer path length increases absorbance.

Step-by-Step Guide to Using the Calculator

  • Input Parameters
  • Calculation Process
  • Interpreting Results
Select which parameter you want to calculate. Enter the known values. The calculator will compute the unknown using the Beer-Lambert Law.
How to Use the Calculator
Use the examples for guidance. Check units and ensure all values are positive and valid.

Usage Tips

  • To find concentration, input absorbance, path length, and molar absorptivity.
  • To find absorbance, input concentration, path length, and molar absorptivity.

Real-World Applications of Beer-Lambert Law

  • Spectrophotometry
  • Pharmaceutical Analysis
  • Environmental Testing
The Beer-Lambert Law is widely used in laboratories to determine the concentration of solutes in solution by measuring absorbance.
Applications in Science and Industry
It is essential in drug development, water quality testing, and biochemical research.

Application Scenarios

  • Measuring protein concentration in a sample.
  • Testing water for contaminants using absorbance.

Common Misconceptions and Correct Methods

  • Myths About Absorbance
  • Best Practices
  • Troubleshooting
A common misconception is that absorbance is always directly proportional to concentration at all ranges. At high concentrations, deviations can occur due to chemical and instrumental factors.
Avoiding Common Pitfalls
Always use the correct units and ensure the solution is homogeneous. Clean cuvettes and calibrate instruments for accurate results.

Misconceptions

  • Nonlinear absorbance at high concentrations.
  • Dirty cuvettes causing inaccurate readings.

Mathematical Derivation and Examples

  • Beer-Lambert Law Derivation
  • Parameter Effects
  • Worked Examples
The Beer-Lambert Law can be derived from the exponential attenuation of light as it passes through a medium. The law is linear for dilute solutions.
Example Calculation
Given A = 0.85, ε = 15000 L·mol⁻¹·cm⁻¹, l = 1 cm, c = ?; c = A / (ε·l) = 0.85 / (15000·1) = 5.67e-5 mol/L.

Calculation Examples

  • Calculate c for A = 0.85, ε = 15000, l = 1.
  • Calculate A for c = 0.002, ε = 15000, l = 1.